The persistence of drug and alcohol seeking is a critical issue in the treatment of substance abuse and dependence. Drug cues figure prominently in current theories of addiction and are thought to play a role in the persistence of drug seeking and relapse. Because drug taking is operant behavior, animal models of drug self-administration based on operant conditioning have been useful in examining how biological and environmental variables contribute to drug seeking and relapse. Methodological and theoretical developments in the study of the persistence of operant behavior in the face of disruption may provide further insights into to the persistence of drug-maintained responding. Behavioral momentum theory provides a set of methods and a quantitative theory of how reinforcement conditions affect the persistence of behavior in the presence of a stimulus. Based on a prediction of behavioral momentum theory, we have found that the persistence of alcohol seeking in the presence of a stimulus depends on all the reinforcers (both drug and non-drug) available in that stimulus, even if some of those reinforcers interfere with drug-seeking. Thus, it may be necessary to consider all of the sources of reinforcement (i.e., drug and non-drug) associated with a drug cue to understand the impact of that cue on the persistence of drug seeking. Further extensions of the methods and quantitative theoretical framework of behavioral momentum theory may provide important insights into the persistence of drug seeking in the presence of drug cues. In addition, because drug cues appear to play a role in relapse, extensions of behavioral momentum theory to an animal model of relapse may provide insights into how the context of reinforcement contributes to relapse in the presence of drug cues. The proposed research aims to: 1) Further examine the effects of alternative non-drug reinforcers on the persistence of alcohol self-administration; 2) Examine the utility of extending the quantitative account of resistance to change provided by behavioral momentum to alcohol self-administration; and 3) Extend behavioral momentum to an animal model of relapse. Continued examination of these issues is important because the persistence of drug seeking is one of the defining features of drug and alcohol abuse. A better understanding of how drug cues impact the persistence of drug seeking may suggest novel behavioral interventions targeted at reducing the impact of exposure to such cues. This project is important to public health because it will help provide an understanding of the factors that make drug and alcohol abuse so persistent. Findings from this project may suggest novel behavioral treatments targeted at reducing the persisence of drug and alcohol abuse and preventing relapse.